High-temperature fan



May 4, 1948. c. NYGREN HIGH-TEMPERATURE FAN Filed Aug. 31, 1945 7 Sheets-Sheet 1 INVENTOR May 4, 1948., c. NYGREN.

HIGH-TEMPERATURE FAN Filed Aug. 31, 1945 7 Sheets-Sheet 2 F. 5 62 as 65 g a y 4, 1948. c. NYGREN HIGH-TEMPERATURE FAN Filed Aug; 31, 1945 '7 sheets sheet 3 gwu lull:

fie yen/0)" 59 Cari 3 F67? MW 1 1948- c. NYGREN HIGH-TEMPERATURE FAN Filed Aug. 31, 1945 7 Sheets-Sheet 5 1 1948-v C.NYGREN 2,441,121

HIGH-TEMPERATURE FAN Filed Aug. 31, 1945 7 Sheets-Sheet; 6

fave/2&2 CargZ A /ygren/ May 4, 1948. c. NYGREN HIGH-TEMPERATURE \IFAN Filed Aug. 31, 1945 7 Sheets-Sheet 7 nae/2502' Gaga/"e20 fa low/2e s.

Patented May 4, 1948 n1 FEED ;;siTAr-E1-s PATENT entice Application' August 31, 1945;:8eiialfNaiSBflfii .5 Claims. I -1 "This invention relates 'toncentrifugal ifans vor blowers and has for its 'principal object to; give the several partsa11 theifreedom-o movement-in expanding and contracting that may be necessary to prevent distortion aiid maintain-dynamic bal ance while providing safe restraint against a broken blades getting-away and working idestruction.

T Generally speaking, this is accomplished :by making the shroud rings ore side :plates :ride or float on the blades-with appropriate-freedom to expand and contract individuallywhile surrounding the edge portions ofthezbla'desand restraining outward movement beyon-d aselected limits.

The inner'portions of .thebladesmay. be made ,fast a tohub members leavingrtheashrouds ito :prevent the escape of an outertportion of'za broken blade,

'or the shrouds may take allxthe stress due to cm- 'trifugal force acting on theblades.

In the accompanying drawings,:several selected f orms, are shown:byswayzofiillustration.

Figs. 1 and ."2 arez'diagrammatic :views of .a double inlet fan and sits associated :parts @in :one

form of installation;

Fig. 3 is a part edge xview :and part vertical section along the: ax-issofzthe: fan embodying'sithe invention;

.at right :anglesxto the axis;

FigJfi is affront viewiof zone of the hubs; .Fig; 9 is asection-through'one' of thehubs along theaxis;

Fig. I; is a sidetview. ofcaiquarterq-segment"of .onezof the shrouds;

Fig. 11 is anedgezviewbfEFigdlO; :Fig. 112 :is :in' :partaan I edge view 1- of. 1a.: difierent sembodimentrand-partrsectionealong theaaxis;

'.*Fig..:13-is=.=an: elevationzofonezof 'thexbladesin L-Figji14 isan end-'viewrofatheiblade lookingfrom the top in Fig. 13;

Fig. Iisza .sideview-of :the-zblade lockingffrom theright inEFig; 13;

-Fig. 16 is in :part'va side' view'ofitheufan shown in Fig. 12 and 'in; part. a:.verticalasectionthrough tthermiddleat right anglestovthe axis;

r'Fighl'i .isxat side view of-zarhalfiasegment of one a ofzthe shrouds;

1 Fig. :l8;.is in .partanzedge viewsand in :part a sec-e 2 ation along the ams-ofzanother embodiment of the invention;

Fig. 19 is.an-elevationiof;.one ofethe bladesshown in Fig. 18; 5 Fig.r20 i s-an-.-end.-view-oi. one. of'zthetblades looka ing; from the top in-Fig. 19;

51155121. is a. side :view of one of the blades looking-from the-right in;Fig.'19,;

Fig. e22,- is, inpartean end elevation .and in? Part .10 :a section. along: the middle: at. right. angles. tothe axisofthe-wheel-shown in Fig.=18

Fig. 23 is in part an edge View and inpartan axial section. .of-a singleinlet fan corresponding .to the.iorm shown-intFigs.-18=22;.;and V Fig. '24 is a sidaview-pf .auarter .segment. of theshroud-at the :closedtsideoi? the fan.

This application is aizcompanion to my-appli- ,cations: Ser. Nos.:536,801, filed May v22, 194=4:,-n0w :Patent No.-; 2,385.,837;.\533,456,.file:dMay 1,1944,

.20 mow-Patent. No.-2,41-5,033 .590,'7.53, filed. April .28,

1945; 594,750,-file d- May.19, 19.45.

In Figs. 1. and. 2, t0 indicatesawconventional .form oif; masonry installation: for a fan or blower within which isametal :casing l l vfor a. double 25 inlet tan t2 mountedvon alhollow water. cooled shaft 1-3 journallediv inbearings -l 4 and: driven. by

:a motor t5 throughaa wbelt drive 16. The shaft is water cooled through. connectionsindicatedat and- 1-8.

.The' detail :of .-a preferred form of double inlet -fan is-show-n in -Figs. 3-11 (Sheets 2 and 3) The fan iscomposed :of twelve-blades, generally indicated at 5! two circulargshrouds- 5|,and two hub port-ions 52 .assembledon -a..-hollow shaftiB.

-.In:Figs. 3--.and 4 -itewill be seen that :each blade 1- is vcornpose'd of :a generally fiat plate having .an .innewportion or? toot 54 twith ;outwardly convergingq'sideaedges z55*by-vir.t-ue of which it becomes somewhat wedge shaped or delta shaped. Each .40 rsideedge 55 is .providedrwith flanges or machining .pads i56, which -,-joinsector-shaped iianges 51, the ;-twelve:oii them? forming 18101116111311 group :between ntheuhub'; portionsil; as: shown=.-in-;Fig. 7. Each o i apedfiangeim isprovidedwithan open- 1 ing 553 ea-lignedwith an, opening =59 yin thaadjacentrvfiange 69 of the hub portionsq52, and :these alignediopenings rreceivefastening idowelypinsfi l 24x0? them positively: iasteningand holdingithe blades against woutward movement under cen- Those pins are .in circular .arrangement about ;ithe taxis :of 1 rotation :and Jin themselves, like the, blades which they fasten, they tend :to establish and .:-maintain idynamic :io'alance.

gphe .-mainbody of: thea'inner portion; onfoot-M of the blade is thickened relative to the outer portion 62, the inner portion being on the order of thick and the outer portion on the order of A" thick. The change in thickness is very gradual to avoid any abruptness, and avoiding abruptness is the rule throughout this fan construction. While no distinct line can be indicated for the change from one thickness to another, the thinner portion of the blade is roughly bounded by the line 63 in Figs. 3 and 4.

The machining pads 56 of the sector-shaped flanges 51 are joined to the inner portions 54 by gently curving fillets 64, generally indicated by shading. In order to provide metal and strength about the inner ends of the openings 58, bosses 65 are provided adjacent to the sector-shaped flanges 51, and they are joined to the thinner inner portions 54 by other gently curving fillets B6. The extreme inner edges 61 of the blades are comparatively straight, and, together, the twelve of them form a sort of polygon around the shaft 53 but spaced from it, as appears in Figs. 3 and '7. The flanges 51 are slightly longer than the intervening portions 54.

At or adjacent to each side edge, each blade is thickened to provide ribs 69 with flat faces 10 to bear against the inner walls of the shrouds At the inner portions of the ribs 59, the blades are provided with hooks H providing openings 12 to receive the shrouds 5l and having shoulders 13 adapted to be opposite the inner peripheries of the shrouds.

Each shroud 5| adjacent to its inner periphery on the outside isprovided with lugs 14, the adjacent faces of which define a passage 15 to receive one of the hooks H as the blades are assembled with the shrouds.

. Each shroud is of uniform thickness except adjacent to the outer edge, where it is tapered, preferably by inclining from the outer side toward the inner'side, as indicated at 16. This tapering reduces weight and places the mass of the metal in a position of advantage to resist the bursting tendencies of centrifugal force on the shroud. In one theory of design, they are considered like a flywheel, and it is assumed that one-half the centrifugal force is resisted by the metal lying along a diameter. Theoretically, therefore, the most eifective distribution would be great thickness at the inner periphery and extreme thinness from there to the outer edge. The form shown is acoinpromise between theoretical perfection and practical necessity.

It will be apparent that the shrouds merely float on the twelve blades with freedom to expand and contract independently, the interlock between the hooks H and the lugs I4 serving to prevent slippage in accelerating and decelerating.

The flange 60 of each hubportion 52 has an inner flat face 11 for contacting with and bearing against the grouped flanges 51' of the blades. Outwardly of this face 11, which is at right angles to the axis, each flange 60 has an inclined face 18 provided with twelve slots 19 to receive and hold the machined faces 56 of the converging edges 5 5 of the inner portions 54 of the blades. While the slots are backed by a considerable thickness of flange metal, the inner portions are rounded at the corners 80 to avoid any abrupt change in surface that might foster cracks. The fit between the sides of the slots and the machined faces 56 is close and, together with the dowel pins 6|, provides a strong driving and holding joint between the hubs and the blades. The adjace t surfaces of the slots 19 and the machined faces 56 being remote from the axis of rotation, minor accumulations of tolerances will have less effect than they would have if those surfaces were close to the axis. Thus, the construction insures accurate and positive placing and holding of the blades in their relatively diverging positions with respect to the hubs in accelerating, driving, and decelerating. This accuracy also contributes to the smooth support of the shrouds on the twelve blades, both in operation and in expanding and contracting.

Each hub portion 52 has a bore to receive the shaft 53 to which it is keyed. The left hub portion 52, as shown in Fig. 3, rests against a shoulder S on the shaft, and the right hub portion is held against the blades by a large locking collar C, made fast by a lock nut N and a lock washer 8! having one tab 82 fitting in one of the key slots in the shaft 53 and other tabs 83 and 84 bent into the respective notches 85 and 86 in the lock nut N and the locking collar C. In initial assembly, the collar C is set up wrenchtight and then backed off enough to provide for expansion, which can be initially determined by calculations and corrected by empirical data.

The fan shaft is water cooled and is made of carbon steel. The hub portions 52 are of suitable alloy. The shaft and hub portions, therefore, have different coefficients of expansion. The tendency thus created to increase the clearance between the hub portions and the shaft as the fan is heated up is greatly augmented by the fact that the shaft is water cooled and the hubs are not. Bearing in mind'that all of the fan is carried by the hubs on the'shaft and that a 30-inch fan, substantially as shown in Figs. 3-11, will weigh on the order of 650 pounds, it is apparent that a slight eccentricity between the hub portions and the shaft results in enormous forces due to lack of dynamic balance. To prevent this condition and to obtain and maintain dynamic balance, three or more keys or splines are used to effect a driving connection between the shaft and the hub portions.

In Fig. 8, three keyways are shown at 120 degrees on centers, and that number will probably bemost used, though four keys at 90 degrees are contemplated. The detail and advantages of this are discussed in my copending application Ser. No. 533,456, filed May 1, 1944.

In this embodiment of the invention, it is contemplated that the pins 6| will establish a circular datum line on which the blades are fastened to the hub members and by which centrifugal force is'resisted. The blades are also held by the intimate relation between the inclined portions 19 of the flanges 60 and the grip on the machined faces 56 of the flanges 55. Hence, even if there should be a break through a blade in'the general area of the pins Bl, the blade would still be held by the flanges 60. If a break should occur beyond the grip of the flanges 60, the outer portion of the blade would be held against centrifugal force by the two shrouds, and thus be prevented from flying on tangentially to the probable destruction of the fan.

The embodiment shown in Figs. 12-47 (Sheets 4 and 5) corresponds to that just described except for a few differences in the connection between the'shrouds and the edges of the'blades. At or adjacent to each side edge, each blade in this latter construction is thickened and provided with grooves I68 whereby at each sideof each groove there are ribs I69 and I'Hljthe ribs I10 being relatively short and the ribs I69 being relatively long. The latter are approximately as long as the shrouds are wide at their edges, and the former are about the depth of the slots in the shrouds.

Each shroud I! is a ring provided with inwardly opening slots 96 adapted to receive the corresponding portions of the blades as the grooves I63 are slipped along the shrouds in assembling the blades by radially outward movement.

With this arrangement, as well as the form shown in Figs. 3-11 (Sheets 2 and 3) the shrouds that float on the blades are compelled to accelerate and decelerate with the blades, but can expand and contract independently of them and without putting any strain on them. They serve as a safety device to hold the outer portion of any blade beyond the hub flanges should the same break away from the inner portion.

Beyond the features described;the other parts in this embodiment shown in Figs. 12-17 (Sheets 4 and 5) correspond to those in the earlier embodiment, and they are indicated by the same reference characters.

In the construction shown in Figs. 18-22, the shrouds are given the duty of resisting centrifugal force in its entirety. This is somewhat extreme, and will probably find its chief usefulness in fans of light duty at relatively low temperatures among furnace fans.

Each blade I56, generally speaking, is a fiat plate with inner extensions I5Ila curved, as best seen in Figs. 20, 21, and 22. Each blade has two feet I5I cylindrical on their inner surfaces to rest upon hub members I52 and secured to them by keys I53. The hub members are keyed to the shaft 53 by three keys I54 to maintain dynamic balance in spite of the differential of expansion, as heretofore explained.

Each blade at each side is provided with laterally extending pins I55 adapted to be received in slots I56 in the shrouds I51, which are held against lateral motion by heads I58 on the pins.

In order to lighten the shrouds, they are cut away between the slots I56, as indicated at I59.

This construction allows freedom of expansion and contraction between the several parts, and

relatively outward movement of the blades is limited by the pins I55 in the slots I56 in the shrouds. They form the datum line and circular arrangement on which the blades necessarily come to rest in establishing dynamic balance.

In Figs. 23 and 24, there is shown a single inlet fan with the hubs and blades constructed and arranged after the fashion illustrated in Figs. 3-17, and the shrouds are interlocked with the blades somewhat after the fashion shown in Figs. 12-16, except that the inner shroud 25I is provided with keyhole slots 252 to receive the lugs 253 by which the blades and the inner shroud are interlocked.

I claim:

1. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with their inner portions converging inwardly toward said axis and their outer portions diverging outwardly from said axis, hub members in driving relation to the inner portions of 6 the blades, a circular shroud at each side of the outer portions of the blades having its inner edge spaced radially outwardly from the hub members and provided with inwardly opening slots aligned with the blades, and projections on the blades engaged in said slots.

2. In a centrifugal fan, a plurality ofblades in circular arrangement about a common axis of rotation with their inner portions converging inwardly toward said axis and their outer portions diverging outwardly from said axis, hub members in driving relation to the inner portions of the blades, a circular shroud at each side of the outer portions of the blades having its inner edge spaced radially outwardly from the hub members and provided with slots aligned with the blades and closed at their outer ends, and projections on the blades engaged in said slots.

3. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with their outer portions diverging outwardly from said axis and their inner portions converging inwardly toward the axis and having segmental flanges forming a circuit about said axis and having inner foot portions provided with outwardly converging side edges, a circular shroud at each side of the outer portions of the blades, projections on the blades engaged with the shrouds to hold them against individual outward movement, and hub members wedged within the circuit of the segmental flanges and having axially inclined opposed surfaces engaging the side edges of the inner foot portions of the blades.

4. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with their outer portions diverging outwardly from said axis and their inner portions converging inwardly toward the axis and having segmental flanges forming a circuit about said axis, an annular shroud at each side of the outer portions of the blades, projections on the blades engaged with the shrouds to hold them against individual outward movement, and hub members engaged with the circuit of segmental flanges on the inner portions of the blades and spaced radially inwardly from the inner edges of the shrouds.

5. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with their outer portions diverging outwardly from said axis and their inner portions converging inwardly toward the axis and each blade having symmetrically oppositely extending segmental flanges at each of its axial edges forming a circuit about said axis, an annular shroud at each side of the outer portions of the blades, projections on the blades engaged with the shrouds to hold them against individual outward movement, and a hub member keyed to each circuit of segmental flanges and spaced radially inwardly from the adjacent shroud.

CARL NYGREN.

REFERENCES CITED UNITED STATES PATENTS Name Date Ferre June 6, 1944 Number 

